WEDNESDAY, Feb. 6 (HealthDay News) -- Older motorcyclists are up to three times more likely than younger riders to be seriously injured in a crash, a new study shows.

The findings are especially important in light of the growing number of older riders, the researchers added.

They analyzed U.S. government data collected between 2001 and 2008, during which time there were 1.5 million motorcycle crashes involving adults aged 20 and older who required emergency department treatment. Men accounted for 85 percent of these cases.

When divided by age groups, more than 921,000 of the incidents involved riders aged 20 to 39, more than 466,000 involved those aged 40 to 59 and more than 65,000 involved those 60 and older, according to the study, which was published online Feb. 6 in the journal Injury Prevention.

Injury rates for all three age groups increased during the study period, but the greatest increase -- nearly 250 percent -- occurred among riders aged 60 and older. Riders in this age group were nearly three times as likely to be admitted to the hospital after a crash than those in their 20s and 30s.

Riders aged 40 to 59 were nearly twice as likely to be admitted to the hospital after a crash than younger riders, according to researcher Tracy Jackson and her colleagues in the department of epidemiology at Brown University, in Providence, R.I.

Compared to younger riders, the risk of serious injury in a crash was 66 percent higher for middle-aged riders and two and a half times higher for those aged 60 and older.

Fractures and dislocations were the most common types of injuries in all age groups, but middle-aged and older riders were much more likely than younger riders to suffer these types of injuries, particularly around the chest and rib cage.

Middle-aged and older riders also were much more likely to suffer internal organ damage, most commonly the brain.

The greater severity of injuries among older riders may be due to age-related physical changes, such as reduced bone strength, decreased elasticity in the chest wall and shifts in body-fat distribution, the researchers said. Underlying illnesses may also increase the risk.

In the United States, the percentage of motorcyclists over the age of 50 more than doubled from about 10 percent in 1990 to 25 percent in 2003. The average age of people involved in a motorcycle crash has steadily increased, with rates of injuries among riders over 65 increasing by 145 percent between 2000 and 2006, according to the study.